核能已经成为一种重要的能源，氘和氚都是未来生产核能的燃料。氚是氢元素的一种原子，氚原子的核电荷数是 [ ]
A．1
B．2
C．3
D．4
答案：A
阅读理解。
Look at this picture. It's a picture of Jim's bedroom. A broom is behind the door. The football is under
the bed. The chair is behind the desk. Some nice flowers are on the desk. Some nice pictures are on the
wall.
1. This is _____.
A. a picture of Jim
B. a bedroom of a picture
C. a picture of a bedroom
2. Where is the broom?
A. Behind the door.
B. Under the desk.
C. Under the bed.
3. We can see the football _____.
A. near the window
B. behind the chair
C. under the bed
4. Some _____ are on the desk.
A. flowers
B. chairs
C. books
5. You can see _____ on the wall
A. a football
B. a chair
C. some pictures
RB投入情况下，单侧空预器跳闸联跳（）。
A、同侧引风机；
B、异侧引风机；
C、同侧送风机；
D、异侧送风机。
wers are on the desk. Some nice pictures are on the